If you have poor ventilation in the heater area, then the furnace burner canpll air down the heater vent and extinguish the pilot. It can also generate carbon monoxide which would also put out he pilot. If you leave the door to the heater area ajar or open and the pilot stays lit, then this is most likely the reason.

: I have a 40 gal Rudd water heater that the pilot light goes out on every night. I can relight it and it seems to stay on until the next morning. I have replaced the thermo coupler but it is doing the same thing. I also have a gas heating unit but no problems with it. Is the thermo coupler the most common problem? What would be the next thing to try?